Book Description

The Galactic Center (GC) is an extremely energetic region, host to a variety of powerful astronomical sources and rare astrophysical processes that emit a large flux of non-thermal radiation. The inner 375x600 pc region, called the Central Molecular Zone (CMZ), is home to the supermassive black hole Sgr A*, massive cloud complexes, supernova remnants, and likely the peak concentration of dark matter in the Galaxy. It has been studied across an extremely wide range of wavelengths by many instruments. In this dissertation, I present the results of my analysis of the very high-energy (VHE) (E > 100 GeV) gamma-ray emission from the GC using data from about 155 hours of quality observations taken with the VERITAS imaging atmospheric Cherenkov telescope. This emission includes a strong central point source VER J1745-290, coincident with the position of Sgr A*, and diffuse emission that extends along the Galactic ridge. VER J1745-290 is detected at a significance of 38 sigma, and I reconstruct its spectrum and lightcurve. Its spectrum is best fit by a power law with an index of -2.16 +/- 0.18 and flux normalization of (11.76 +/- 2.03)e-12 TeV/cm2/s at 1 TeV, and an exponential cutoff at 10.8 +/- 3.0 TeV. The exponential cutoff in its spectral shape, along with its apparent lack of variability in the very-high-energy gamma ray range favor electron models of its emission, such as the plerion model of emission from the pulsar wind nebula G359.95--0.04. I also present the results of my analysis on the morphology and, for the first time with VERITAS, the spectrum of diffuse emission in the GC. I find an approximately 52\% correlation of the gamma signal to molecular gas as traced by CS(1-0) line emission. I report an energy spectrum that is best fit by a pure power law with a hard index of -2.26 +/- 0.13, showing no evidence of a cutoff over 40 TeV. This strengthens the evidence of a potential accelerator of PeV cosmic rays being present in the GC. Using these results, I discuss the impact on current models of diffuse emission and possible connections to the central source. I also provide detections and spectra of other sources within the field of view of VERITAS.